If you are interested in Windows 7, you can download until 31.10.2009 the FULL german VERSION of the book "Windows 7 auf einen Blick" from MS-Press for free! (i am not sure if there is a english version for free too)
Download Full Version: http://register.microsoft-press.de/ (http://register.microsoft-press.de/) (350 pages @ 29 MB)
Free german preview: http://download.microsoft-press.de/?id=chapter (http://download.microsoft-press.de/?id=chapter)
(http://register.microsoft-press.de/images/book.gif)
There is no download link on the site. You have just to enter your email-adress and you will get an email with a direct download link for the pdf!
Nice find, im sure there must exist an English version either US or UK.